Abstract
When a piscine anesthetic, 2-amino-4-phenylthiazole, was absorbed by rainbow trout, Salmo gairdneri irideus, from an anesthetic solution, a whole body concentration of 6.7 and 13 ppm was attained at 3 hours. and 6 hours, respectively. After anesthetization for 6 hours, fish were transferred into 500l of fresh water flowing at a rate of 2l per minute. The anesthetic previously absorbed by the fish was excreted into the environmental water by this process. Residues of the anesthetic in the fish were measured by gas chromatography-mass spectrometry (GC/MS). The total concentration of anesthetic in the fish declined at a rate comparable to that predicted by a computed theoretical biexponential curve obtained by a previously described mathematical procedure. The biological half-life of the anesthetic under these experimental conditions was approximately 40 minutes in the primary step and 22 hours in the secondary step. The whole body residues which remained at 24 and 48 hours were 0.1 ppm and 0.05 ppm, respectively.
